Lactic acid bacteria bacteriocins as novel antimicrobials against antibiotic-resistant Streptococcus pneumoniae in opthalamic infections.

BACKGROUND

Ophthalmic infections, including conjunctivitis and keratitis, caused by Streptococcus pneumoniae may lead to significant ocular morbidity. Rising antibiotic resistance among ocular pathogens has reduced the efficacy of conventional treatments highlighting the need for alternative antimicrobial strategies. This study aimed to evaluate the antimicrobial potential of bacteriocins produced by lactic acid bacteria (LAB) against antibiotic-resistant Streptococcus pneumoniae isolated from clinical ophthalmic samples and to compare their efficacy with conventional antibiotics.

METHODS

A total of 230 eye swab samples were collected from patients attending Rashid Latif Medical Complex (RLMC), Lahore, Pakistan. S. pneumoniae isolates were identified using morphological, biochemical, and 16 S rRNA gene sequencing methods. Antibiotic susceptibility was performed using the agar well diffusion method. LAB strains from milk, curd, and pickle samples were identified by 16 S rRNA sequencing and screened for bacteriocin-mediated inhibitory activity against S. pneumoniae. Bacteriocin concentrations were quantified using the Bradford assay, and molecular weight was determined by SDS-PAGE.

RESULTS

Four S. pneumoniae isolates exhibited varying resistance patterns, including resistance to ciprofloxacin and gentamicin. LAB strains, particularly Enterococcus faecium and Ligilactobacillus salivarius, demonstrated inhibitory activity against S. pneumoniae, with inhibition zones of up to 8.6 mm. Bacteriocin concentrations ranged from 3.55 to 7.17 µg/mL, with an estimated molecular weight of ~ 3.5 kDa.

CONCLUSION

LAB-derived bacteriocins exhibit promising antibacterial activity against antibiotic-resistant S. pneumoniae, suggesting their potential as cost-effective and sustainable alternatives to conventional antibiotics for ophthalmic infections. Further studies on purification, formulation, and in vivo evaluation are required to advance bacteriocin-based therapeutics toward clinical application.